Diversity of Arctic pelagic <i>Bacteria</i> with an emphasis on photoheterotrophs: a review

Abstract

Abstract. The Arctic Ocean is a unique marine environment with respect to seasonality of light, temperature, perennial ice cover, and strong stratification. Other important distinctive features are the influence of extensive continental shelves and its interactions with Atlantic and Pacific water masses and freshwater from sea ice melt and rivers. These characteristics have major influence on the biological and biogeochemical processes occurring in this complex natural system. Heterotrophic bacteria are crucial components of marine food webs and have key roles in controlling carbon fluxes in the oceans. Although it was previously thought that these organisms relied on the organic carbon in seawater for all of their energy needs, several recent discoveries now suggest that pelagic bacteria can depart from a strictly heterotrophic lifestyle by obtaining energy through unconventional mechanisms that are linked to the penetration of sunlight into surface waters. These photoheterotrophic mechanisms may play a significant role in the energy budget in the euphotic zone of marine environments. Modifications of light and carbon availability triggered by climate change may favor the photoheterotrophic lifestyle. Here we review advances in our knowledge of the diversity of marine photoheterotrophic bacteria and discuss their significance in the Arctic Ocean gained in the framework of the Malina cruise.

Bacterial communities in Arctic first‐year drift ice during the winter/spring transition

“…In the upper ice horizons, increased permeability may have aided the bacteria to utilize the EPSs produced during the winter and/or other carbon sources frozen in ice during the autumn freeze‐up, as also discussed previously (Riedel et al, ; Deming, ). Another, yet very speculative, survival strategy of bacteria under nutrient limitation and salinity stress may be their ability to obtain supplementary energy from light via light‐harvesting pigments (e.g., proteo‐ and xanthorhodopsins; Feng et al ., ; Palovaara et al ., ) as well as bacteriochlorophyll a (Koh et al ., ; Boeuf et al ., ), which are found throughout the major sea‐ice bacterial classes, such as Flavobacteriia, Gammaproteobacteria and Alphaproteobacteria (Koh et al, ; Vollmers et al ., ). Bacterial genera from these classes, potentially possessing light harvesting pigments were also abundant at all three stations in our study.…”

High turnover rates of aerobic anoxygenic phototrophs in European freshwater lakes

“…AAP bacteria are abundant in various marine environments (Kolber et al, , Cottrell et al, , Sieracki et al, , Jiao et al, , Yutin et al, , Boeuf et al, ) and also in many freshwater lakes and rivers (Mašín et al, , Mašín et al, , Ruiz‐González et al, , Čuperová et al, , Caliz and Casamayor, , Fauteux et al, , Lew et al, ). Freshwater AAP bacteria seem to represent a diverse assemblage of species belonging exclusively to different subgroups of Alpha‐ and Betaproteobacteria (Waidner and Kirchman, , Shi et al, , Salka et al, , Čuperová et al, , Caliz and Casamayor, ).…”

Bacterial community structure in a sympagic habitat expanding with global warming: brackish ice brine at 85–90 °N

“…According to most previous studies carried out in the Arctic Ocean [12,71,79], as well as in Antarctic seas [80], Cyanobacteria seem to be practically absent from sea ice and surface SW. Initially we detected various sequences that were classified as Cyanobacteria, but these were later identified as chloroplasts.…”

“…Similarly, bacterial community composition in the SW of the Arctic shelf LMEs is quite variable at the class level [12,71]. The differences may partly be attributed to environmental variability on temporal (seasonal) or spatial (coastal vs. open ocean) scales, or if the sea was ice-covered or not, but often there does not seem to be any clear pattern.…”

“…However, low temperature should not be a restriction for the occurrence of Cyanobacteria [82], e.g., coccoid picocyanobacteria have been reported in several studies from Arctic coastal regions [71,[83][84][85][86]. It has been argued that the Cyanobacteria reported from the Arctic Ocean represent allochthonous influences from land [87].…”